Development of Zeise's Salt Derivatives Bearing Substituted Acetylsalicylic Acid Substructures as Cytotoxic COX Inhibitors.

Zeise's salt derivatives of the potassium trichlorido[η2-((prop-2-en/but-3-en)-1-yl)-2-acetoxybenzoate]platinate(II) type (ASA-Prop-PtCl3/ASA-But-PtCl3 derivatives) were synthesized and characterized regarding their structure, stability, and biological activity. It is proposed that the leads ASA-Prop-PtCl3 and ASA-But-PtCl3 interfere with the arachidonic acid cascade as part of their mode of action to reduce the growth of COX-1/2-expressing tumor cells. With the aim to increase the antiproliferative activity by strengthening the inhibitory potency against COX-2, F, Cl, or CH3 substituents were introduced into the acetylsalicylic acid (ASA) moiety. Each structural modification improved COX-2 inhibition. Especially compounds with F substituents at ASA-But-PtCl3 reached the maximum achievable inhibition of about 70% already at 1 µM. The PGE2 formation in COX-1/2-positive HT-29 cells was suppressed by all F/Cl/CH3 derivatives, indicating COX inhibitory potency in cellular systems. The CH3-bearing complexes showed the highest cytotoxicity in COX-1/2-positive HT-29 cells with IC50 values of 16-27 µM. In COX-negative MCF-7 cells, they were 2-3-fold less active. These data clearly demonstrate that it is possible to increase the cytotoxicity of ASA-Prop-PtCl3 and ASA-But-PtCl3 derivatives by enhancing COX-2 inhibition.

Development of methylated cobalt-alkyne complexes with selective cytotoxicity against COX-positive cancer cell lines.

Derivatives of the cytotoxic cyclooxygenase (COX) inhibitor [(prop-2-ynyl)-2-acetoxybenzoate]dicobalthexacarbonyl (Co-ASS) with a methyl group in the 3, 4, 5, or 6 position of the acetylsalicylic acid (ASS) scaffold were synthesized with the aim to achieve enhanced selectivity for COX-2. From this modification, a higher specificity for COX-2-expressing tumors is expected, preventing COX-1-mediated side effects. The cobalt-alkyne complexes were tested for their COX-inhibitory and antiproliferative properties as well as their cellular uptake. Methylation reduced the effects at the isolated COX-1, whereas those at the isolated COX-2 remained nearly constant compared to Co-ASS. In cellular systems, the new compounds showed superior cytotoxicity toward the COX-positive HT-29 colon carcinoma cells than cisplatin. The reduced growth-inhibitory potency in T-24 cells, which express distinctly fewer COX enzymes (COX-1/COX-2 = 50/1) than HT-29 cells (COX-1/COX-2 = 50/50), and the only marginal activity in COX-negative MCF-7 breast cancer cells point to an interference in the arachidonic acid cascade through COX-2 inhibition as part of the mode of action, especially as the cellular uptake was even higher in MCF-7 cells than in T-24 cells. These findings clearly demonstrate that the methylated cobalt-alkyne complexes possess promising potential for further development as reasonable alternatives to the limited platinum-based antitumor agents.

Synthesis, characterization and biological activity of bis[3-ethyl-4-aryl-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(i) complexes.

A series of bis[3-ethyl-4-aryl-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(i) complexes (2a-f) containing methyl, fluoro or methoxy substituents at various positions in the 4-aryl ring was synthesized and evaluated for their anti-cancer properties in A2780 (wild-type and Cisplatin-resistant) ovarian carcinoma as well as LAMA 84 (imatinib-sensitive and -resistant) and HL-60 leukemia cell lines. The bis-NHC gold(i) complexes were more active compared to their related mono-NHC gold(i) analogues and reduced proliferation and metabolic activity in a low micromolar range. With the exception of 2d (3-F), the compounds displayed higher potency than the established drugs Auranofin and Cisplatin. The lack of effects against non-cancerous lung fibroblast SV-80 cells indicated a high selectivity towards tumor cells. All tested complexes generated reactive oxygen species in A2780cis cells; however, the induction of apoptosis was very low. Furthermore, thioredoxin reductase is not the main target of these complexes, because its inhibition pattern did not correlate with their biological activity.

In vitro evaluation of cytotoxic effects of di (2-ethylhexyl) phthalate (DEHP) produced by Bacillus velezensis strain RP137 isolated from Persian Gulf.

Phthalates are widely used in polymer science and have potential toxicity related to their chemical structures. However, lots of evidence indicate that phthalate derivatives are undoubtedly produced as secondary metabolites by organisms, including plants, animals, and microorganisms. In the present study, Bacillus velezensis strain RP137 was cultured under optimized conditions. Its biomass was extracted with ethyl acetate with one fraction showing cytotoxic properties. A pure compound was isolated from the active fraction using combined silica gel and LH20 size exclusion column chromatography. Structural evaluation including FT-IR, 1H NMR, 13C NMR, HR-MS and CHN analysis identified the purified compound as di(2-ethylhexyl)phthalate (DEHP) with the formula C24H38O4 and the molecular weight of 389.29 Da. The microorganism-derived (stereospecific) DEHP was strongly reduced the proliferation and induced cytotoxic effects on various eukaryotic cell lines in compare to the synthetic racemic mixture of the compound when assessed by MTT assay. Furthermore, crystal violet assay and morphological changes confirmed the cytotoxic effect of DEHP. Interestingly, non-malignant SV40-immortalized fibroblast cells were less affected by the purified DEHP. Further evaluation on the antibacterial activity of DEHP documented no effect toward Gram-positive (S. aureus) and Gram-negative (E. coli and P. aeruginosa) pathogens even at a high concentration of 100 µM. In conclusion, existence of DEHP as byproduct of microorganism's metabolism can seriously be considered as a warning to human health.

Amide and ester derivatives of chlorido[4-carboxy-1,2-disalicylideneaminobenzene]iron(iii) as necroptosis and ferroptosis inducers.

In continuation of the structure-activity study about 4-substituted chlorido[N,N'-disalicylidene-1,2-phenylenediamine]iron(iii) complexes as necroptosis and ferroptosis inducers, we introduced a 4-COOH group at the 1,2-phenylenediamine moiety of the lead ([Fe(iii)salopheneCl]) and derived the resulting complex 15 to the respective ethyl, propyl, or butyl amides (16-18) and esters (19-21). The compounds 16-21 exerted concentration-dependent antiproliferative and antimetabolic effects against HL-60 cells. The esters were more active than the analogous amides. Elongation of the alkyl chain enhanced the activity of the amides, while that of the esters decreased. The complexes 16-21 induced necroptosis and/or ferroptosis but not apoptosis. Studies on protein binding and uptake into HL-60 cells indicated that the complexes mainly accumulated by passive transport. The high binding tendency of all complexes to apo-Transferrin, however, points to participation of a carrier-mediated transport into the cells, too.

Synthesis, characterization and biological activity of bromido[3-ethyl-4-aryl-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(i) complexes.

Bromido[3-ethyl-4-aryl-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(i) complexes (8a-h) with methoxy, methyl and fluorine substituents at different positions of the 4-aryl ring were synthesized and characterized. The relevance of the 2-methoxypyridin-5-yl residue and the substituents at the 4-aryl ring with regard to the activity against a series of cell lines was determined. Particularly against the Cisplatin-resistant ovarian cancer cell line A2780cis, the most active bromido[3-ethyl-4-(4-methoxyphenyl)-5-(2-methoxypyridin-5-yl)-1-propyl-1,3-dihydro-2H-imidazol-2-ylidene]gold(i) complex 8c was more active than Auranofin. It also inhibited thioredoxin reductase more effectively and induced high amounts of reactive oxygen species in A2780cis cells. Furthermore, its influence on non-cancerous SV 80 lung fibroblasts was lower than that of Auranofin. This fact, together with a high accumulation rate in tumor cells, determined on the example of MCF-7 cells, makes this complex an interesting candidate for further extensive studies.

A New Approach in Cancer Treatment: Discovery of Chlorido[N,N'-disalicylidene-1,2-phenylenediamine]iron(III) Complexes as Ferroptosis Inducers.

Chlorido[N,N'-disalicylidene-1,2-phenylenediamine]iron(III) complexes generate lipid-based ROS and induce ferroptosis in leukemia and neuroblastoma cell lines. The extent of ferroptosis on the mode of action is regulated by simple modifications of the substituents at the 1,2-phenylenediamine moiety. In HL-60 cells, the unsubstituted lead exclusively caused ferroptosis. For instance, a 4-F substituent shifted the mode of action toward both ferroptosis and necroptosis, while the analogously chlorinated derivative exerted only necroptosis. Remarkably, cell-death in NB1 neuroblastoma cells was solely induced by ferroptosis, independent of the used substituents. The effects were higher than that of the therapeutically applied drug cisplatin. These data clearly demonstrate for the first time that not only iron ions but also iron salophene complexes are potent ferroptosis inducers, which can be optimized as antitumor agents.